Frame for semiconductor package

ABSTRACT

A frame F for semiconductor package has die-pads  3  supported with suspending leads  2  of individual lead frames  10.  Semiconductor devices are arranged on die-pads  3.  These semiconductor devices are collectively molded with molding compounds, and then the collectively molded semiconductor packages are cut into individual packages by means of dicing saw. In the frame F, suspending leads are formed into fish tails, wherein at least one of longitudinal grid-lead and transverse grid-lead is eliminated within areas enclosed with fish tails of the suspending leads  2.  Accordingly, whether R-shape generated by producing frame for semiconductor package by etching process is large or small, to exist metal piece at edges of semiconductor packages in dicing becomes almost nothing.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to a frame for semiconductorpackage in which a semiconductor device is mounted on a lead frame andthe outside thereof, particularly the upper surface of semiconductordevice is encapsulated with molding compound.

[0003] 2. Description o the Prior Art

[0004] In recent years, it has been required to miniaturize and shapesemiconductor product mounted on a substrate thinner, as packaging ofsemiconductor is made denser. It has been severely required for LSI toreduce the number of chips by improving integration level and tominiaturize and make a package lighter. The popularization of so-calledCSP (Chip Size Package) is rapidly advancing. Particularly, in thedevelopment of thin semiconductor product with lead frame, thesemiconductor package of single side encapsulation type has beendeveloped in which a semiconductor device is mounted on a lead frame andthe surface of semiconductor device mounted on a lead frame isencapsulated with molding compound.

[0005]FIG. 1 is a sectional view of one example of semiconductorpackage. FIG. 2 is a plan view thereof. The semiconductor package shownin FIGS. 1 and 2 is comprised of a lead frame 1, a semiconductor device4 mounted on die-pad 3 supported with suspending leads 2 of lead frame1, metallic thin wires 6 electrically connecting electrodes provided onthe top face of the semiconductor device 4 with terminals 5 of leadframe 1, respectively and molding compound 7 for encapsulating theoutside region of semiconductor device 4 including the upper side ofsemiconductor device 4 and the lower side of die-pad 3. Thesemiconductor package is of non-lead type in which so-called outer leadsare not projected from the semiconductor package and the two of innerleads and outer leads are integrated into terminals 5, wherein used leadflame 1 is half-cut by etching in such a manner that die-pad 3 ispositioned higher than terminals 5. Since such a step is formed betweendie pads 3 and terminals 5, molding compound 7 can be inserted into thelower side of die-pad 3 so that a thin semiconductor package can berealized even though the semiconductor package has non-exposed die-pad.

[0006] Since semiconductor device is miniature, a matrix type frame ismainly used for the above-mentioned semiconductor package of non-leadtype, in which plural semiconductor devices are arranged in a directionof a width of the matrix type frame. Further, recently, from a demandfor cost down, it is thought to switch over a frame of individuallymolding type shown in FIG. 3 to a frame of collectively molding typeshown in FIG. 4.

[0007] In the frame of individually molding type, as shown in FIG. 3(A),individual molding cavities C of small size are provided separatelywithin a frame F. After molding, individual semiconductor packages arestamped out so that semiconductor packages S shown in FIG. 3(B) areobtained. Namely, semiconductor devices are mounted on die-pads of leadframes through silver paste and others, and wire bonding is carried out.Thereafter, respective semiconductor devices are individually moldedwith molding compound and the respective molded semiconductor devicesare stamped out to form individual semiconductor packages.

[0008] In the frame of collectively molding type, as shown in FIG. 4(A),some molding cavities C of large size are provided within a frame F.Multiple semiconductor devices are arranged in matrix within eachmolding cavity C, respectively and collectively molded with moldingcompound. Thereafter, the collectively molded semiconductor devices arecut at grid-leads L by means of dicing saw so that a semiconductorpackage S shown in FIG. 4(B) is obtained. Namely, semiconductor devicesare mounted on die-pads of lead frames through silver pastes and othersand wire bonding is carried out. Thereafter, plural semiconductordevices arranged are collectively molded with molding compound to agiven cavity size, and then the collectively molded semiconductordevices are cut to form individual semiconductor packages by dicing.

[0009] In the above-mentioned semiconductor package of collectivelymolding type, heat generated in semiconductor device is transmittedthrough a die-pad to suspending leads, in which there is a case wheresuspending leads come off from molded resin due to a difference inthermal expansion coefficient between metal and resin. Therefore, inorder to prevent the coming-off of suspending leads suspending leads areformed with projection portions, or as shown in FIG. 2, the tips ofsuspending leads are formed into a forked shape, so-called fish tailshape.

[0010] Generally, in case of producing products by etching, partsdesigned to be form a right angle are finished to have roundish shape(R-shape), no matter how etching process is carried out. In a frame forsemiconductor package of collectively molding type having suspendingleads formed into fish tail shape. R-shape formed by etching is alsoseen. For example, even if suspending leads 2 having fish tail shape aredesigned as shown in FIG. 5, etched products have R-shape as shown bythe dotted line.

[0011] Semiconductors are mounted on the frame F for semiconductorpackage of collectively molding type, collectively molded, thereafterdivided into individual semiconductor packages by dicing. At this time,if roundish part of R-shape does not come to dicing line α there is noproblem. However, if roundish part of R-shape comes to dicing line αbecause of large R-shape, as shown in FIG. 6, a metal piece 8 ofgrid-lead L is left at an edge of individual semiconductor package.Further, in a few cases, when mounting semiconductor product on asubstrate, the metal piece 8 comes off from molded resin and drops downon the substrate, so that a state where accident such as shot circuit islikely to occur is generated.

BRIEF SUMMARY OF THE INVENTION

[0012] An object of the present invention is to provide a frame forsemiconductor package of collectively molding type used for theproduction of semiconductor package, in which the frame forsemiconductor package is formed in such a manner that any metal piece isnot left at edges of semiconductor device in dicing.

[0013] In order to achieve the above-mentioned object, a frame forsemiconductor package of the present invention comprises plural leadframes arranged in matrix through grid-leads, in which the individualsemiconductor devices are mounted on die-pads supported with suspendingleads of the individual lead frames, respectively, the semiconductordevices are collectively molded with molding compound and thecollectively molded semiconductor devices are cut at grid-leads by meansof dicing saw to obtain individual semiconductor packages, wherein thesuspending leads are formed into fish tails and at least one oflongitudinal grid-lead and transverse grid-lead is eliminated withinareas enclosed with fish tails of the suspending leads.

BREIF DESCRIPTION OF THE DRAWINGS

[0014]FIG. 1 is a sectional view of one example of semiconductorpackage.

[0015]FIG. 2 is a plan view of semiconductor package shown in FIG. 1.

[0016]FIG. 3 is an explanatory view of a frame of individually moldingtype.

[0017]FIG. 4 is an explanatory view of a frame of collectively moldingtype.

[0018]FIG. 5 is an explanatory view of R-shape generated by etching.

[0019]FIG. 6 is an explanatory view showing a state where metal piece isleft at edges of semiconductor package.

[0020]FIG. 7 is a plan view of one example of the present invention.

[0021]FIG. 8 is a partial enlarged view of the frame shown in FIG. 7.

[0022]FIG. 9 is a sectional view of another example of frame showncorresponding to FIG. 8.

DETAILED DESCRIPTION

[0023] Then, referring to figures, embodiments of the present inventionsare explained. FIG. 7 is a plan view of one example of a frame of thepresent invention. FIG. 8 is a partial enlarged plan view of the frame.

[0024] In these figures, F designates a metal frame for lead frames, inwhich lead frames 10 are arranged in a matrix of 3×4 through grid-leadsL. The grid-leads L connect terminals 11 of adjacent lead frames 10 witheach other. In each lead frame 10, die-pad 3 is supported withsuspending leads 2. Further, suspending leads 2 are formed into fishtail and both the longitudinal grid-lead L and transverse grid-lead Lare eliminated within areas enclosed with fish tails of the suspendingleads 2.

[0025] Process for producing semiconductor packages using the frame F isas follows. First, semiconductor devices are mounted on die-pads 3 ofthe respective lead frames 10 of frame F through silver pastes and wirebonding is made between terminals 11 of lead frames and electrodesprovided on the top face of semiconductor devices. Thereafter, twelvesemiconductor devices are collectively molded with molding compound to agiven cavity size and then the collectively molded semiconductor devicesare cut at grid-leads L by means of dicing saw in such a manner thatterminals 5 of individual lead frames are left, by which thecollectively molded semiconductor devices are divided into individualsemiconductor packages. In this dicing, edges of semiconductor packageare formed with resin cut into an orthogonal shape, since nothing existsexcept molded resin at edges X of each semiconductor device.

[0026]FIG. 9 is a partial enlarged plan view of another example showncorresponding to FIG. 8.

[0027] In this case, transverse grid-lead L is eliminated within areasenclosed with fish tails of suspending leads 2. Semiconductor devicesare mounted on the frame F for semiconductor packages and collectivelymolded with molding compound. Thereafter the collectively moldedsemiconductor devices are cut at dicing lines a by means dicing saw toform individual semiconductor packages. Even though longitudinalgrid-lead L exists outward at each edge X of individual semiconductorpackage, this part is not roundish. Therefore, edges of semiconductorpackage are formed with mounted resin cut into orthogonal shape.

[0028] As above-mentioned, a frame for semiconductor package of thepresent invention comprises plural lead frames arranged in matrixthrough grid-leads, in which individual semiconductor devices aremounted on die-pads supported with suspending leads of the individuallead frames, respectively, the semiconductor devices are collectivelymolded with molding compound and the collectively molded semiconductordevices are cut at grid-leads by means of dicing saw to obtainindividual semiconductor packages, wherein the suspending leads areformed into fish tails and at least one of longitudinal grid-lead andtransverse grid-lead is eliminated within areas enclosed with fish tailsof the suspending leads. Accordingly, whether R-shape generated byproducing frame for semiconductor package by etching process is large orsmall, to exist metal piece at edges of semiconductor packages in dicingbecomes almost nothing. Accordingly, when mounting semiconductorproducts on a substrate, there is no case where metal piece drops out onthe substrate, so that accident of short circuit occurs.

What is claimed is:
 1. A frame for semiconductor package comprisingplural lead frames arranged in matrix through grid-leads, in whichindividual semiconductor devices are mounted on die-pads supported withsuspending leads of the individual lead frames, respectively, thesemiconductor devices are collectively molded with molding compound andthe collectively molded semiconductor devices are cut at grid-leads bymeans of dicing saw to obtain individual semiconductor packages, whereinthe suspending leads are formed into fish tails and at least one oflongitudinal grid-lead and transverse grid-lead is eliminated withinareas enclosed with fish tails of the suspending leads.